Can You Avoid the Clouds?
I fly IFR on just about every cross-country trip I make, a practice I started shortly after I got my instrument ticket in the mid-1990s. At first, like most new instrument pilots, I filed on sunny, VFR days to get the hang of flying the airways, communicating with the controllers and interpreting the instruments. All of that was before moving maps were ubiquitous, so it took a lot of craft to make it come out right, which it usually did.
My biggest impression after doing this for a while, even on days with a benign high overcast or slightly lower broken layer, was that flying IFR made trip planning a lot easier and the execution of the trip a relative piece of cake because I didn’t have to struggle to stay clear of clouds. If one appeared where I hadn’t expected it to be, I’d just fly through it. Nothing could be simpler — not to mention safer.
When you’re VFR, however, it can get really complicated really fast. Here’s a common scenario: You’re a relatively new VFR pilot and you planned a flight from KXYZ to KABC, intending to cruise at 5,500 feet heading eastbound toward the destination. You picked that altitude in order to have adequate terrain clearance over the mountains in that direction, and it worked fine for the planning phase since it also gave you some clearance under the forecast layer. You preflight, taxi, take off and start the climb.
However, shortly after departing on the climb, you realize the layer is lower than forecast, by quite a bit, it seems, and there seem to be multiple layers, the first one looking a lot more like “broken” than “scattered,” as had been forecast. As you continue the climb you realize you can’t make it to 5,500 feet without being partially in that broken/scattered layer — should you try anyway and dodge the clouds you do encounter? Or should you accept a lower altitude? While the odd altitude of 3,500 feet is OK for now, it will give precious little clearance when the mountains start, and there are peaks slightly higher than that, at least you think so, and the clouds seem to be getting a bit lower as you proceed. By the time you’re in the mountains, you’ll be in Class G, so you only need to be clear of clouds, right? As far as terrain is concerned, well, you still have a little while before you need to worry too much about that, right? Once the terrain starts rising, you can climb a bit if need be because you’ll still have adequate clearance over the terrain — at 3,000 feet agl or below you don’t have to comply with the cruise altitude rules, right? — at least you think that’s what the regs say.
If you have any experience, you soon realize you are unwittingly putting yourself into a few different traps. First, you are putting yourself at risk of not being able to maintain terrain clearance under the layer. When that happens, especially if you encounter rising terrain, as on this hypothetical mission, all bets are off.
Avoiding terrain requires only a few hypothetically simple things: knowing where you are laterally, where the terrain is in relationship to you, what the height of the terrain is and what altitude you are maintaining (if, indeed, you can maintain that altitude without entering the clouds). These all sound straightforward, but they are not.
The problem is that once you start trying to avoid the clouds, it’s easy to lose track of where you are in two dimensions over the ground. Before the advent of moving map displays, this is where pilots would get hopelessly lost in faceless terrain flashing by through holes in the clouds. All too often, the next loud sound they heard was their last.